Combination of photometric and RGB filters to highlight dark nebulae
Photographing dark nebulae is a fascinating challenge for astrophotographers, often posing difficulties due to the low brightness and high contrast between celestial objects and dark nebulae. This often requires the use of different techniques and exceptionally dark skies to bring out fine details in the dark nebular structures.
In this test report, we examine the photographic results and the effectiveness of the combination [product sku="cmosSLOANset" style="imgright"] und [product sku="cmosRGBset"] to evaluate its effectiveness in improving contrast and detail, as well as enhancing them in all their colorful glory, while maintaining natural color reproduction.
Equipment used:
All single frames and the final image were taken with a [product sku="1931096" style="imgleft"]and the Celestron RASA 11“ as well as a selection of 9 different filters, which were changed manually using the UFC (Univeral Filter Changer) System.
The entire system was controlled and monitored by the N.I.N.A. imaging software. Filters were changed manually using the UFC Filter Changer. After each filter change, an automatic focusing motor was used to refocus (always after 90 minutes or sooner if the temperature dropped rapidly) in order to always hit the perfect focus point. Flat frames were taken at the end of the filter session BEFORE each filter change.
Gain settings:
High Gain Mode Gain 0 / Offset 25 (for all wideband exposures) High Gain Mode Gain 56 / Offset 25 (for narrowband exposures)
Acquisition conditions and software:
The images were taken far from optimal conditions under city skies. With an exposure time of over 70 hours, spread over all filters, the images were taken on every clear night with good seeing conditions between May 2023 and July 2023. The main image shows the reflection nebula Van den Berg (vdB) 152 in the constellation Cepheus together with the very faint and diffuse molecular cloud LDN 1217 (LDN = Lynds Dark Nebula). The object is also known among astrophotographers as "Wolf's Cave Nebula".
Details on filter applications:
Photometric filters to increase contrast:
The use of photometric filters in combination with RGB-Filters led to a significant increase in contrast in the dark nebulae regions. The use of SLOAN g‘, SLOAN r‘ and SLOAN i‘ improved the visibility of fine structures and details, while RGB filters preserved the natural colors.
The three central filters used for the Sloan Digital Sky Survey (SDSS) divide the spectral range into three roughly equal parts: g': 410nm to 550nm, r': 555nm to 695nm, and i': 695nm to 845nm. These filters are therefore the perfect choice for three-color imaging with modern cameras.
Wavelength range of the Celestron RASA 11": The manufacturer specifies the Celestron RASA 11“ with an optimized wavelength range of 400 to 700nm. However, the test with the SLOAN i‘ Filter (695-845nm) clearly shows that a sharp and detailed image is also possible far beyond the fully corrected range. The prerequisite for this is refocusing after each filter change.
Filters for the reduction of light pollution:
The application of the [product sku="uhcl" style="imgright"], as well as the IDAS LPS-P2, were used to capture the luminance images. The UHC-L booster filter, which was also specially designed to reduce light pollution, led to a considerable improvement in image quality. The sky appeared darker, which significantly increased the contrast to the dark nebulae. In combination with the LPS-P2 luminance filter, this led to better recognition of fine details and structures.[br]
Use of the f/2 Ultra-HighSpeed H-alpha narrowband filter:
By integrating the narrow-band [product sku="cmosHaUltraHighspeed" style="imgright"] certain emission lines could be selectively emphasized. The hydrogen regions, which are rather weak for color filters, could be precisely extracted and re-inserted into the final color image in the subsequent image processing. This helped to enhance the structures around the dark nebula and the H-alpha regions.
Combination of RGB filters for natural colors:
Using RGB-Filters alone tended to reduce the contrast between the sky and dark nebulae. The integration of photometric filters helped to increase this contrast, while RGB filters preserved natural colors and allowed for a balanced color appearance.
Overall appearance and aesthetic gain:
The combination of photometric and RGB-Filters resulted in impressive structures within the dark nebula LDN 1217, emphasizing the fine details and structures while preserving the natural colors, resulting in an aesthetically pleasing and well-balanced image.
Red Green Blue SLOAN g‘ SLOAN r' SLOAN i' UHC-L IDAS LPS-P2 H-Alpha f/2 3.5nm
3.25 hours (195 x 60”) 3.15 hours (190 x 60“) 3 hours (180 x 60”) 5.4 hours (325 x 60”) 6.3 hours (380 x 60”) 8.5 hours (340 x 90”) 6.4 hours (385 x 60”) 12,7 hours (1525 x 30”) 21.5 hours (645 x 120”)
Note from Baader Planetarium: The following article was kindly provided to us by Christoph B. for publication.
Discover this 2.1M Classic Slit Dome also on our World Map[br]
Background
My journey to establishing my own observatory began with an extraordinary heirloom, a Baader observatory dome over 30 years old, carrying its own remarkable history. This dome had been in the possession of Mr. Ernst Blättler (✝) for decades, who had donated it to his club, the Astronomical Society of Zürcher Oberland (AGZO), some years ago. Until his old age, he was active as a passionate demonstrator. A few years ago, however, the club expressed the desire to operate a modern dome with the latest technology, which could be remotely operated by the club members.
Therefore, the club ordered a new 2.1m split dome, which was installed in September 2020. The heirloom, the over 30-year-old manually operated dome, was kindly left to me by AGZO. This dome, a testament to artisan craftsmanship and enduring quality, thus came into my possession and offered me the unique opportunity to transform it into a functional, modern observatory – a project that not only reflected my passion for astronomy but also a deep appreciation for astronomical heritage.
The challenge was to restore this historic dome, which had observed the sky for decades, and equip it with modern technology. It was a journey full of technical, physical, and emotional challenges. This dome had its own personality – shaped by its past, age, and many stories it had collected over the years. My goal was to not only breathe new life into it but also transform it into a modern observatory that could utilize the latest astronomical technologies.
Refurbishing the Classic Baader Dome
Restoration and Construction
The restoration of the dome was a mix of challenge and passion. Thanks to the know-how and materials from my brother-in-law's boatyard, I was able to breathe new life into the dome. The dome quality was impressive, and after replacing the rubber parts and rollers and repairs to the gelcoat, the dome shined like new.
In May 2023, I was finally able to start assembling the dome. The previous months were marked by continuous rain, which slowed down the excavation, formwork, and reinforcing work. I chose self-leveling pump concrete for the foundation, as direct access for a conventional concrete mixer was impossible. Within 10 minutes, the nearly 2.5 cubic meters of concrete were poured, and after two weeks, I could de-shutter. Then in early June, the dome and mount were set up in one day.
Foundation PreparationsFinished Foundation with Self-Leveling Pump ConcreteAssembling the Dome
Technical Challenges
An important step was determining the precise position of the pillar. I had previously set up all the equipment in the dry in the shed to test the positioning. After Baader Planetarium warned me about the dimensions of the large refractor in a 2.1m dome, I left nothing to chance. A few days after the dome was set up, the mount and finally the telescope were installed and both were put into operation. More on this below.
The GM 3000 HPS on the Baader Steel PillarMy CFF 185mm APO on the GM 3000 HPS MountThe Finished Dome Shines in New Splendor
Weather Resistance and Practical Test
The dome was already exposed to extreme weather conditions, including a heatwave of over 36° C and two thunderstorms, one with 120 km/h winds and heavy rain. The dome withstood, and thanks to the replacement seal kindly provided by Baader Planetarium for free, the interior remained dry.
As already mentioned, I am thrilled at how well the dome could be renovated. Although it was a lot of work as mentioned above, without the substance of the object, the best polishing machine is useless. And the substance of the dome is first-class.
State-of-the-Art Instruments
Commissioning the Mount
The mount, a 10Micron GM3000 HPS, was another crucial factor. The commissioning was surprisingly simple:
I started with a short drift alignment as I was used to, and already saw that there was no PE. Then I conducted a 10-point alignment with Mount Wizzard 4. After adjusting Polaris and generating a 60-point model, I was impressed with the precision and performance of the mount. The images in long exposures, such as 15 minutes on M101, were visually and metrically flawless – only turning the dome made me sweat.
First 60-Point Model45 minutes later 3.1 RMS and 55” PA ErrorFirst Target, 10 min. exposed: WOW – absolutely round starsNext Target: M101 15 min exposed, still round measured starsThird Object NGC 6888 - 20 min exposed on the other pier side
First Astronomical Successes
After these results on the first evening, I was overwhelmed. The mount enables absolutely precise and clear shots, commissioning completed successfully in one night! Particularly impressive were the results in unguided long exposures.
In the following weeks, I stayed with the Crescent Nebula and was able to collect 7h Ha and OIII with 10min subs each, as well as 14*3min RGB for the stars. All un-guided! Below I show the first finished processed image, for a First Light I am already extremely satisfied.
NGC 6888 – 7h Ha and OIII with 10min subs and 14x3min RGB
Final Remarks
As you can see, I am thrilled so far. The 30-year-old dome is brilliant and now shines again in full splendor – the mount alone could already become a hobby. The next project step will be the automatic rotation of the dome, so I don't have to turn it every 15 minutes – but this is currently only in the planning phase.
I am extremely pleased that this dome with a long history will continue to serve me well for many years.
Sure, here's the English translation:
FROM A FOUND OBJECT TO A MODERN OBSERVATORY: THE STORY OF MY "ANTIQUE" BAADER DOME Note from Baader Planetarium: The following article was kindly provided by Christoph B. for publication.
Discover this 2.1M Classic Split Dome also on our world map Background My journey to establishing my own observatory began with an extraordinary heirloom, a Baader observatory dome over 30 years old, carrying its own remarkable history. This dome had been in the possession of Mr. Ernst Blättler (✝) for decades, who had donated it to his club, the Astronomical Society of Zürcher Oberland (AGZO), a few years ago. Until his old age, he was active as a passionate demonstrator. A few years ago, however, the club expressed the desire to operate a modern dome with the latest technology, which could be remotely operated by the club members.
Therefore, the club ordered a new 2.1m split dome, which was installed in September 2020. The heirloom, the over 30-year-old manually operated dome, was kindly left to me by AGZO. This dome, a testament to artisan craftsmanship and enduring quality, thus came into my possession and offered me the unique opportunity to transform it into a functional, modern observatory - a project that not only reflected my passion for astronomy but also a deep appreciation for astronomical heritage.
The challenge was to restore this historic dome, which had observed the sky for decades, and equip it with modern technology. It was a journey full of technical, physical, and emotional challenges. This dome had its own personality - shaped by its past, age, and many stories it had collected over the years. My goal was to not only breathe new life into it but also transform it into a modern observatory that could utilize the latest astronomical technologies.
Refurbishing the Classic Baader DomeRestoration and Construction The restoration of the dome was a mix of challenge and passion. Thanks to the know-how and materials from my brother-in-law's boatyard, I was able to breathe new life into the dome. The quality was impressive, and after replacing the rubber parts and rollers and repairs to the gelcoat, the dome shined like new.
In May 2023, I was finally able to start assembling the dome. The previous months were marked by continuous rain, which slowed down the excavation, formwork, and reinforcing work. I chose self-leveling pump concrete for the foundation, as direct access for a conventional concrete mixer was impossible. Within 10 minutes, the nearly 2.5 cubic meters of concrete were poured, and after two weeks, I could de-shutter. Then in early June, the dome and mount were set up in one day.
Foundation Preparations
Finished Foundation with Self-Leveling Pump Concrete
Assembling the Dome
Technical Challenges An important step was determining the precise position of the pillar. I had previously set up all the equipment in the dry in the shed to test the positioning. After Mr. Risch warned me about the dimensions of the large refractor in a 2.1m dome, I left nothing to chance. A few days after the dome was set up, the mount and finally the telescope were installed and both were put into operation. More on this below.
The GM 3000 HPS on the Baader Steel Column
My CFF 185mm APO on the GM 3000 HPS Mount
The Finished Dome Shines in New SplendorWeather Resistance and Practical Test The dome was already exposed to extreme weather conditions, including a heatwave of over 36 degrees and two thunderstorms, one with 120 km/h winds and heavy rain. The dome withstood, and thanks to the replacement seal kindly provided by Baader Planetarium for free, the interior remained dry.
As already mentioned, I am thrilled at how well the dome could be renovated. Although it was a lot of work as mentioned above, without the substance of the object, the best polishing machine is useless. And the substance of the dome is first-class.
State-of-the-Art InstrumentsCommissioning the Mount The mount, a 10Micron GM3000 HPS, was another crucial factor. The commissioning was surprisingly simple:
I started with a short drift alignment as I was used to, and already saw that there was no PE. Then I conducted a 10-point alignment with Mount Wizzard 4. After adjusting Polaris and generating a 60-point model, I was impressed with the precision and performance of the mount. The images in long exposures, such as 15 minutes on M101, were visually and metrically flawless – only turning the dome made me sweat.
First 60-Point Model
45 minutes later 3.1 RMS and 55” PA ErrorFirst Target, 10 min. exposed: WOW – absolutely round stars
Next Target: M101 15 min exposed, still round measured stars
Third Object NGC 6888 - 20 min exposed on the other pier sideFirst Astronomical Successes After these results on the first evening, I was overwhelmed. The mount enables absolutely precise and clear shots, commissioning completed successfully in one night! Particularly impressive were the results in unguided long exposures.
In the following weeks, I stayed with the Crescent Nebula and was able to collect 7h Ha and OIII with 10min subs each, as well as 14*3min RGB for the stars. All un-guided! Below I show the first finished processed image, for a First Light I am already extremely satisfied.
NGC 6888 – 7h Ha and OIII with 10min subs and 14x3min RGBFinal Remarks As you can see, I am thrilled so far. The 30-year-old dome is brilliant and now shines again in full splendor – the mount alone could already become a hobby. The next project step will be the automatic rotation of the dome, so I don't have to turn it every 15 minutes – but this is currently only in the planning phase.
I am extremely pleased that this dome with a long history will continue to serve me well for many years.
Acknowledgments
I would like to thank AGZO for generously leaving the dome to me and especially Baader Planetarium for their support and the provided seal. Without their products and their service, I could not have realized this project. My dream of owning my own observatory has become a reality.
Christoph B., November 2023
Takahashi is known for excellent telescopes, but when it comes to adapting accessories, they sometimes go their own way, which can make life hard for astronomers. In particular, the use of a bino viewer on the Takahashi Mewlon kept raising questions, and since we don't sell Takahashi telescopes, we couldn't simply try it out ourselves.
Thus, we are all the more grateful to our customer Maiko, who was able to successfully use the [product sku="2456460"] with his Mewlon 180 C and gave us feedback on his setup. We thank him for the information and would like to briefly present the required parts here.
At the Mewlon 180 C, he used:
[product sku="2458130"]
[product sku="2456005"]
[product sku="2456313A"]
[product sku"=2456314Z"]
[product sku="2456460"]
Takahashi Mewlon 180 C with MaxBright II Bino-Viewer
Of course, it is not just a matter of adapting the bino viewer mechanically, you also have to come into focus – on the Mewlon, the 1.25x glass path corrector is sufficient for this. Another advantage of a glass path corrector: it picks up the light beam "further back" in the telescope, where the beam of light is narrower, so that vignetting is avoided.
And how does it work under the night sky? Here, this combination fulfills the expectations, as the following observation report proves.
We thank Maiko for the information about the adaptation to the Mewlon and wish him many clear nights!
Observing with the Mewlon 180 C on the roof top. May 17th/18th 2023
Actually, yesterday would have been a much better night for the first deep sky session with the Mewlon 180 C: My SQM showed values of 21.2 to 21.3 MPSAS – and that on the roof top in the middle of a small town! The Milky Way was clearly visible and structured, which corresponded probably to a good Bortle 4 sky.
Well, I had to use the following night: The SQM showed 20.6 MPSAS, the Milky Way was barely structured, slightly blurred, probably between Bortle 4 and Bortle 5.
MaxBright®II Bino and Rigel Quickfinder at the Mewlon 180 C
For moon and planets, I tested the combination of HEQ 5, Mewlon 180 C and the Baader bino-setup, consisting of MaxBright II, BBHS T2 prism, 1.25 x GPC, ring dovetail and heavy-duty changer a few times. With the Panoptic 24mm and the Nagler 12mm T4, which were modified to 1.25", there were good to very good moments for observing the moon. During the brief moments of good seeing, the view is breathtaking. Unfortunately, I have been waiting in vain for good seeing (lasting longer than a few seconds) so far this year. Last August and September I had conditions that made for wonderful Jupiter and Saturn observations (at that time still monocular), also from the roof. Saturn appeared almost like in a photo at 240x in the 9mm Nagler, at about 20° height above the horizon. Several years before, I had a spectacular view of the moon with the Mewlon in April at 180x: contrast and sharpness were overwhelming, the image as if cut out... so I hoped that this spring the seeing would play along... well, maybe when the morning visibility of Saturn and Jupiter begins. After setting up the telescope and finishing the polar alignment, I wanted to start with M3, but had no success. So I tried M13 and struggled, until finally I had it in the eyepiece. Why? Because of GoTo-refusal or purism...
To be able to use the setup binocular and without GoTo, I had to solve some problems. When pointing the telescope to a new object, the system must be in good balance, because the clamps are loosened. But this only works if the bino is always in the same position. I decided to align it to the axles of the mount. But this blocks the 30mm finder. I roughly locate the object in the Rigel finder I have attached. Then I clamp the axles. Now the bino can be carefully rotated into observation position. The Mewlon viewfinder can then be used for more precise adjustment, with corrections made via the motors.
This works fine for moon and planets, but I would not recommend this method for deep sky objects. Besides the usual observing problems, the limited visibility of the objects in the mewlon viewfinder and the necessary bending of your body to look into both finders cause lots of frustration when you have to guess in the Mewlon's viewfinder in which direction the invisible target has to be moved relative to the invisible crosshairs by the tracking motors which move only at snail's pace.
Ready to go: Monocular and binocular configuration
You're better of searching the objects monocularly with a long focal length 2" eyepiece, so that the object is in the field of view when switching to the bino-viewerrn.
Well, M13 was a delight in the binoviewer at about 110x: A quite dark sky background, and countless little stars in a cluster. At 220x the image naturally became quite dark.
M92 was a dream. I caught myself saying: "What a cute little bunch." On the same telescope, 220x was more usable, but not really good either. I mean, this magnification is better suited for the moon and planets in nights with really good seeing.
For a higher magnification in the bino-viewer, which is for medium seeing or brighter deep sky objects, I will probably try 16/17mm eyepieces, as 16mm will give you about 169x...There was something very touching about being able to enjoy M92 resolved into stars with both eyes almost meditatively on the roof garden of my small town at 3 o'clock in the morning.
The Mewlon is best known as a telescope for planets, but I encourage you to try bright, compact deep sky objects.
Monocularly, I had beautiful observations of M13, M92, M57 and the Eskimo Nebula in the Mewlon under a medium Bortle 4 sky.
Bino-viewers are also often praised for planetary and lunar observation.
Here, too, I recommend trying brighter deep-sky objects at the Mewlon. It can be very rewarding.
Since I am observing without GoTo, it is important for me to be able to quickly switch between the bino viewer and a 2" eyepiece to find objects more easily. I have now found a working combination for this too:
Mewlon 180 C on HEQ 5 in tracking-only mode monocular vs Baader PlanetariumMaxbright II
It seems that my Mewlon setup is now ready to suit my observing style.
My equipment:
Mewlon 180 C upgraded with Rigel Quickfinder
ScopeStuff FineFocusKnob
mirror diagonal Televue Everbrite 2“
LVW 42mm, Nagler 22 T4, Nagler 12 T4 eyepieces
Baader Planetarium Maxbright II Bino-viewer, GPC 1,25 x, Zeiss Heavy Duty Quick Changer, T2-BBHS Prism
Panoptic 24mm eyepieces and Nagler12mm T4, modified for 1,25“
First night, June 11th, 2023, starting shortly after midnight:
My goal with the Mewlon was to find a solution to be able to quickly switch between mono and bino observations. On the one hand, I want to be able to observe optimally adapted to the conditions, on the other hand, I want to give fellow observers the option of going the "easier" way of monocular observation, and then to be able to observe effortlessly with a bino-viewer. In addition, I have developed the ambition to find objects in the classic way without a goto-mount with the setup described and to be able to observe either monocularly or binocularly.
The observation site is my small-town roof garden, which provided me several nights of very good seeing.
At dusk, I set up my telescope relaxed in a T-shirt – tt must have become summer... I used the Kochab method to polar-align the telescope. I used the the Celestron power tank as power source. My first object was M13. I found it quite easily with Rigelsucher and the LVW 42 eyepiece. Then I switched to the bino: M13 was beautiful to see for a short time, then fog moved in. The focus difference between mono ans bino is noticeable, but far from dramatic. In all configurations I reach focus effortlessly.
I paused, relaxed, looked a few times through the telescope. Eventually the fog cleared and I looked for M13 again. At 113x it was quite respectable in the 12mm Nagler. In about 30 minutes, the cluster remained reasonably in the centre of the field of view, which speaks for an acceptable polar-alignment.
M3 was a bit harder to find, but finally I succeded. Not very impressive at 113x and quite low in the sky...
On the other hand, M92 was a beauty: resolved into fine stars in the bino-viewer, again at 113x. It is wonderful to be able to experience this from the roof at home! Only a welcome-back-party of the neighbours distracted me a little.
After a break, I tried my luck at Saturn. Around 3:30 it was a little over 15° high above the horizon, of course still too low. But still it was quite pleasant at 113x, with a few quiet moments every now and then. Then I bravely tried the 12mm eyepieces at 225x. Surprisingly, there were quite passable phases despite the bad seeing. Cassini division, ring shadow, and colours of the cloud bands were well visible. I'll get back to Saturn when the conditions are better. Saturn was one reason to use a bino-viewer with the Mewlon. Oddly enough, at 225x it didn't seem that big to me.... if only the seeing was a bit more reliable...
All in all, it's a successful start. It's wonderful what is possible when using both eyes and combining Takahashi and Baader.
Every now and then I read about back-focus problems. I would like to encourage you to find out on your own Mewlon whether it is possible to successfully use a bino-viewer, and also use it for deep sky.
It seems to work very well for me.
Maiko
What do you look for in an astronomical filter? Everyone has different requirements and goals and with a myriad of filters available today; how do you choose the right filters to unleash the full potential of Astrophotography?
In this blog our customer Ian Aiken gives some high level advice on what to look for when choosing a filter, coupled with reasoning why he choose the Baader's CMOS-Optimized LRGBand Ultra Narrowband f/2 filters, along with example LRGB and SHO images taken with these filters on his Celestron RASA 11 from his Bortle 7 suburban location.
Blog Post by Ian Aiken:
I live in the North East of England in the United Kingdom, which experiences a temperate maritime climate characterized by mild summers and cool winters. Cloudiness can vary throughout the year and it feels like I only get 20 usable clear nights per year at my Bortle 7 location during the 6 months where astronomical darkness actually occurs. I've been an Astrophotographer for over 20 years and I've had all kinds of telescopes, mounts, filters (including Optolong, Astro Hutech, Chroma, Baader) and cameras (Atik, QHYCCD, ZWO, Canon) in this time, for both planetary and deep sky photography. Financially, I've learnt the hard way through fine tuning my current collection to something which supports my sky conditions, budget, time, and imaging goals.
Currently I own a Skywatcher EQ8 mounted in my roll off roof observatory. On this I have a RASA 11 with Baader UFC, QHY268M camera and Baader's CMOS-Optimized LRGB and Ultra-Narrowband f/2 filters.
Here are the factors I've considered when choosing my filters:
Price: Assess the price of the product in relation to its features, quality, and performance. Is the price reasonable and competitive compared to similar products in the market? Consider whether the product offers significant advantages or unique features that justify its price.
In my opinion, Baader filters are absolutely value for money. They've kept the price competitive and performance high. A set of Baader filters costs a little more than a single Chroma. Chroma are good, but did not feel value for money in comparison (Baader 2" LRGB set ~ € 500 vs. Chroma LRGB ~ € 2.238).
Quality: Examine the quality of the product. Does it meet your expectations in terms of durability, craftsmanship, and overall build quality? A product that is well-made and built to last will provide better long-term value.
Baader CMOS-Optimized filters come with Baader Planetarium's Life-Coat technology. Baader warrant the coatings for the life of the filter guaranteeing that the coatings will not peel, flake or physically degrade and they have no issues with you cleaning the filters with fine optical cleaning equipment. You can see the build quality is high, the coatings look durable, and I can understand how Baader can offer such a life time warranty. I don't think anyone else offers this.
Performance: Evaluate how well the product performs its intended function. Does it deliver the expected results or fulfil your requirements? Consider its efficiency, accuracy, reliability, and any additional benefits it provides compared to alternative options.
I'm going to post some images later in this blog, and you can judge the quality for yourself. Yes, there were initial problems with halos and these have been resolved. I haven't had any issues that I am concerned about. Halos can be a real pain, and it's not always the filter that causes this (most cases it is not the filter). Reflections can occur in your imaging system and could be caused by a number of factors: including spacing between optical elements; distance to CMOS camera; the CMOS camera front window itself etc. You have to spend time to understand your entire optical system and its individual nuances.
Features and Specifications: Review the features, specifications, and capabilities of the product. Are there any unique or advanced features that differentiate it from competing products? Determine whether these features are essential to your needs and whether they justify the price.
I opted for high-speed ultra-narrowband to match with my RASA 11. This was based upon my needs (explained a bit further below). In terms of features, what stood out was the features integrated into the filters to help prevent reflections and halos. For instance:
Reflex-Blocker - with coatings to reduce halos caused by my imaging system.
Parfocal - this helps to not have to refocus so much during a filter change. As a filter change is manual on my RASA 11 with the Baader UFC system, it means less movement with my motorised focuser and I am back to imaging quicker (and the focuser isn't off on some mission to reach focus by going further out of focus, which can happen when using an SCT type design).
Blackened edges - again to help reduce reflections in my imaging system, lots of mirrors and glass = high potential for reflection
Sealed Coating Edge - each filter is coated individually and not cut from a sheet. This is probably why they will last forever, and Baader are able to offer Life-Coat warranty.
Brand Reputation and Customer Reviews: Research the brand's reputation and customer reviews of the product. Look for feedback from other customers who have used the product to gain insights into its performance, reliability, and customer satisfaction. Positive reviews and a strong brand reputation can indicate better value for money.
Baader Planetarium have been in business since 1966. I've never experienced any poor customer care from dealers or Baader directly (I admit, I've not really had any issues either, with exception of one issues with the early Baader Steeltrack software which was swiftly resolved by Baader themselves). As a family run business, I feel they are passionate with what they do, and want to do the right thing at the right price, making astronomy accessible to all budget types, and truly are Aiders in Astronomy (this is their slogan).
Longevity and Future Compatibility: Consider the product's longevity and future compatibility. Will it remain relevant and usable for a reasonable period? Assess whether the product is upgradable or compatible with future advancements or technologies to ensure its value over time.
I have the older Baader 2" CCD filters which are in the same condition that I purchased them in. I have no concerns about the longevity of the Baader CMOS Optimised filters, especially backed by the Life-Coat warranty. 2" filters are going nowhere, and while the sensors on modern CMOS cameras are getting larger, I cannot see the need to upgrade anytime soon. I've been using 2" filters for the past 20 years.
Warranty and Customer Support: Evaluate the warranty offered by the manufacturer and the availability of customer support. A reliable warranty and responsive customer support can provide additional value by offering peace of mind and assistance in case of any issues or defects.
Baader offers Life-Coat, a lifetime warranty on their CMOS-Optimized filters (providing used and handled correctly). As a family run business operating for over 50 years, Baader are trustworthy and offer great customer support.
Personal Needs and Preferences: Finally, consider how well the product aligns with your specific needs, preferences, and intended use. Different products may cater to different requirements, so it's essential to choose one that best suits your circumstances and priorities.
What did I choose?
I decided on the Ultra Narrowband High-Speed filters on my RASA 11. Why? Well, the reasoning may surprise you. While the filters are excellent value for money, my garden backs onto other gardens and my neighbours have lots of LED lights lit, especially on weekends when it's not windy, the moon is not out, and the sky conditions are good. You can picture the challenges already. Also, there are trees which do not belong to me which get in the way. I work full time, and have two small children, time is limited. I'm middle-aged, but not retired, so I cannot stay up all night imaging into the early hours. So, I went for a RASA for high speed imaging, reducing my imaging time significantly. While I may image across multiple nights, I don't need to. It just works for my current situation. The Baader filters are brilliant on the RASA 11, and I'm able to produce some excellent results (see further in the blog) even with all my challenges.
I hope the above helps you make a decision on what filters would be good for your needs. Baader Planetarium has a really nice tool to help you match which filters would be best for your imaging system. At time of writing you can access this tool: Baader Narrowband-/Highspeed Filter Selector
Example of Astrophotography taken with Baader CMOS Optimized Filters
I could talk about how tight the stars are (they are), how the filters have much more contrast than their predecessors (they do), but this can still be very subjective and influenced by sky conditions. My skies aren't great, they really aren't, and I have to battle with all the other issues living in a suburban environment. These images were also shot in reasonably poor conditions with thin haze. I also have to point out that I don't spend a massive amount of time processing my images. I think partly, if you capture good data you can produce a good image. You don't, in my opinion, need to push an imagine in processing so that it looks so bright and colourful. To me this looks over processed, and I prefer the darker looking style images with simple histogram and curves transformations. There's the disclaimers out of the way.
My workflow consists of using PixInsight to Calibrate, Stack, Automatic Background Neutralisation, BlurXterminate, NoiseXterminate, and maybe StarXterminate. I may use TGV Denoise post stretching but haven't on these examples. I simply use the ScreenTransferFunction (STF) in PI applied to the Histogram, and a hint of Curves Transformation before exporting off into a PNG/JPG. There's probably so much more I could do, but I don't. Oh, I nearly forgot. I do use PhotometricColorCalobration in PixInsight, which applies a white balance to the image.
NGC 7023 - The Iris Nebula 2 hour integration from Bortle 7 sky
NGC 7023, also known as the Iris Nebula, is a captivating and visually striking celestial object located in the constellation Cepheus. This reflection nebula lies approximately 1,300 light-years away from Earth, and its unique features have made it a favourite target for amateur and professional astronomers alike. The Iris Nebula gets its name from the distinct shape and appearance of its central region, which resembles an iris or an eye. This prominent feature is created by a dense cloud of interstellar dust, which scatters and reflects the light emitted by nearby stars. The dust particles in the nebula also create intricate dark filaments, adding to its overall visual allure. At the heart of NGC 7023 lies a young star cluster, illuminating the surrounding gas and dust with its intense radiation. This interaction gives rise to the vibrant hues of blue and yellow seen in many astro photographs of the nebula.
Imaging System: QHY286M CMOS Camera mounted on RASA 11 with Baader UFC. Filters: Baader CMOS Optimised LRGB Mount: Skywatcher EQ8 Exposure Details: 30 x 60 seconds each channel (LRGB). Total 2 hours integration time from Bortle 7 skies.
NGC 7023 - Baader UV IR CMOS-Optimized used for Luminance in LRGB image.NGC 7023 - Baader R CMOS-OptimizedNGC 7023 - Baader G CMOS-OptimizedNGC 7023 - Baader B CMOS-OptimizedNGC 7023 - LRGB with Stars (I'm not sorry for not pushing the colour on this)NGC 7023 - LRGB reduced StarsNGC 7023 - LRGB without StarsNGC 7023 - LRGB without Stars (OK - I pushed the colour saturation a little!)
NGC 7635 - The Bubble Nebula 17 Hour Integration from Bortle 7 Sky
NGC 7635, famously known as the Bubble Nebula, is a captivating and visually stunning emission nebula located in the constellation Cassiopeia. Its unique structure and distinct appearance have made it a popular target for both amateur and professional astronomers. The Bubble Nebula derives its name from the spherical bubble-like structure at its center, which is created by the powerful stellar wind and radiation emitted by a massive, hot, and young central star. This star, known as BD+60 2522, is estimated to be several times more massive than our Sun and emits intense ultraviolet radiation, which ionizes the surrounding hydrogen gas. The ionized gas then emits light, creating the striking reddish glow seen in images of the nebula.
Imaging System: QHY286M CMOS Camera mounted on RASA 11 with Baader UFC. Filters: Baader CMOS Optimised 3.5/4nm f/2 Ultra Highspeed (Ultra-Narrowband) filters. Mount: Skywatcher EQ8 Exposure Details: Ha: 354x60s, SII: 121x60s & 104x120s, OIII: 175x120s. Total ~17 hours integration time from Bortle 7 skies.
Don't ask why the varying exposure! I'd also like to collect more data on SII and OIII in due course given it's about half of what I planned and need. You can tell by the images more is needed. Maybe next time, right? Astrophotography is for life not just for Christmas, or something like that…
I mixed the combination using PixelMath in PixInsight.
NGC 7635 - Baader f/2 3.5nm Ha CMOS-OptimizedNGC 7635 - Baader f/2 4nm OIII CMOS-OptimizedNGC 7635 - Baader f/2 4nm SII CMOS-OptimizedNGC 7635 - RGB/SHO Combination with StarsNGC 7635 - RGB/SHO Combination with Reduced StarsNGC 7635 - RGB/SHO Combination without StarsNGC 7635 - RGB/SHO Combination Crop
And finally to finish off, M45 taken with Baader CMOS-Optimized LRGB on same kits as above.
M45 taken with Baader CMOS-Optimized LRGB
The Universal Filter Changer (UFC) system with its solid mechanics and high flexibility has found a large user base worldwide. Nevertheless, there are always applications that are not covered by the adapters available to date. Therefore, we receive requests for technical drawings from our customers again and again. In the course of further development of our products, we are now pleased to be able to provide the UFC Design Guide.
This design guide contains technical drawings with all the relevant dimensions you need to make your own adapters for both sides of the UFC - be it S70 ring dovetail connection on the telescope- side or the eyepiece/camera-side adaptation:
UFC Design-Guide: Telescope-side UFC adapter Download as PDF
This means that you can now easily design your own adapters for the UFC system and thus implement individual solutions for your special requirements.
We created this small design guide because of the following review by one for our customers. This is a good example of how your feedback and customizations help us continuously improve our products.
He published a very positive review of our UFC system, which highlighted the solidity and flexibility of the UFC system, but also his need for special adaptations, which motivated us to publish these drawings. Our customer has already created his own adapter using our design guide and kindly provided us with pictures as well as his self-created CAD drawings and documentation for it (without warranty), which we are allowed to share here. He himself writes about it:
My new adapter is an off axis guider for the UFC with M68 connection. It is supposed to connect the 2 1/2" corrector of my selfmade Newton (M68 mount) to the UFC and the camera without mechanical compromises. Another design criterion was to realize a clear aperture as large as possible to minimize the vignetting of a full format sensor. Since I had already made very good experiences with a homemade off-axis guider with an M48 connection, I used the Baader information on the UFC to make an M68 off-axis guider with a UFC ring mount that has the required length for my image train. As prism I used a simple 8x8 prism from Chin.
We encourage you to share your similar projects and customizations with us and our customers. Your feedback helps us to continuously improve and enhance our products.
Thank you for your support and trust in Baader Planetarium.
This summer we provided our customer Mr. Rüdiger Proske with the new [product sku="1363080"] for a comparison test with the longer TZ-4. Most interesting was the question how the TZ-4S, which was primarily designed for the SunDancer II H-alpha filter, harmonizes with his large SolarSpectrum H-alpha filter. We are very happy about his very positive conclusion and his field report.
Please read the detailed report of Mr. Rüdiger Proske here:
In June 2023 I was offered the opportunity to test the new "Baader SunDancer II Telecentric System TZ-4S" (short TZ-4S) for the upcoming market launch.
Since I had already been working with the classic, long telecentric systems TZ-4 and TZ-3 for 2 years, my interest and curiosity for this TZ-4Short were immediately aroused. I wanted to know how the new system had developed and how it compared to the older TZ-4. It was also very interesting to see how the TZ-4S, which was primarily designed for the SunDancer II H-alpha filter, would work with the SolarSpectrum filter, which was used here.
The test setup
The new TZ-4S was tested on a TEC 140 ED with a native focal length of 980mm in front of a SolarSpectrum Solar Observer 1.5 - 0.5A H-alpha filter. To get the refractor to the necessary focal length aperture ratio of F=30, the TZ-4S is ideally suited. The achieved focal ratio of F=28 is sufficient.
A camera with a Sony IMX174LLJ was used as sensor, which is particularly suitable for solar images due to the global shutter. A Baader D-ERF was mounted in front of the telescope lens to keep the energy out of the telescope.
Unboxing and mechanical impression
Baader SunDancer II Telecentric System TZ-4SComparsion new and old TZ-4
The TZ-4S comes in a small, Baader-typical cardboard box. When you hold it in your hands, the TZ makes a solid and robust impression. Spontaneously, one is reminded of an eyepiece, and it can be mistaken for one at first glance. Although it is completely made of metal, it is a bit lighter with approx. 250g than the old system with approx. 310g.
What immediately stands out positively is the compact and short design compared to the significantly longer old system. The satin black surface seems to be identical to that of an eyepiece and promises longevity. Both ends are securely closed by dust caps.
Integration into the image train
On the telescope side, the TZ-4S is inserted into the eyepiece clamp like a 1.25" or 2" eyepiece. I use a 2" Baader ClickLock eyepiece clamp. This allows for quick setup and offers the ability to rotate the H-alpha system as needed.
On the camera side, the TZ-4S has a T-2 thread. This makes it easy to adapt standard components such as T-2 extension tubes or quick-changer. But also an integration into the Baader M68 Tele-Compendium is possible. A minimum of 100mm after the last lens element is specified as backfocus. The distance is usually achieved with T-2 extension tubes. Here I have made the experience that it is quite beneficial to the image quality to increase the distance a little. In the end, I found about 150mm to be optimal. However, the system is very tolerant, as is typical for a TZ (in contrast to Barlow lenses).
The short backfocus is a significant advantage over the old TZ-4, which required at least 240mm as working distance. This significantly reduces the enormous length that an H-alpha setup has. This reduces the load on the focuser and reduces the risk of a mechanical collision during meridian flip.
The entire assembly proved to be mechanically robust with no play or "wobble".
Optical performance
As always, pictures say more than a thousand words. Therefore, I refer you to the pictures below. Visually, however, it can be clearly said that the new system is at least equal, if not superior, to the old one. A direct comparison at Lucky-Imaging is always a bit tricky, since conditions are constantly changing and ultimately a statement is always based on the "stacked" images. However, what I could determine in a direct comparison is that the new TZ-4S was consistently a tad sharper and the images had more reserves in terms of dynamic range. This is probably primarily due to the recalculation of the optical setup and the H-alpha wavelength optimization, which pays off here.
Size comparsion old and new TZ-4(S) at the telescope
Conclusion
The new "Baader SunDancer II Telecentric System TZ-4S" is a wonderfully compact and high-quality telecentric system that feels at home on both small and large telescopes. Its connection options allow for versatile use. And when stowed away, the system takes up no more space than an eyepiece.
To me, the new TZ-4S represents a consistent and logical evolution of its several-year-old predecessor.
Pros:
Compact
Relatively light
Robust
Standard connections
Very short working distance for TZ systems
Cons:
None found in two weeks of use
Notes:
The test system was provided on loan by Baader Planetarium. Many thanks for this!
The system was not tested with the SunDancer II, but with a SolarSpectrum.
Our customer Mr. Karrer uses the [product sku="2301003"]. With his fantastic images Mr. Karrer proves that a SC telescope can keep up with the best refractors in solar photography. We are truely impressed – high-res images which compete with well-known professional observatories.
Read here the detailed field report of Mr. Michael Karrer about the Baader Triband SC 9.25":
I own the Baader 9.25 triband SC telescope now since august 2022, but I'm still not using it often enough. Last May, a calm weather phase was coming and I decided to to start working later in the morning than usual and take a look at the sun instead. Visually, there were no air turbulences visible in the small Lunt H-Alpha telescope, the image was "steady". Accordingly, I had high hopes for the camera view through the 9.25" Triband. For the first time I used the 3x Baader SunDancer telecentric system which I had just bought, which allows a quite short image train. Because everything had to go quickly, I saved myself the warm-up phase of the Solar Spectrum H-Alpha filter and used the etalon of a PST instead. The image on the monitor was the steadiest I have ever experienced! And that at around 7 m focal length! Not much later, I had the AVI data on the hard disk. "Autostakkert" selected the best zones as usual.
I compared my results with (the few) top solar photographers who work with refractors with up to 9" aperture: Details with the Triband-SC are at least on the same level, if not even better to recognise! A sensational result for me! A large refractor costs a lot, is heavy, is hardly transportable and requires a massive mount. With the "feather weight" of an SC, all this is no longer necessary.
Let these pictures be the prove that an SC telescope can keep up with or surpass the best refractors in solar photography (be sure to look at the photos in full resolution).
And if you don't know it better, you sometimes do things which are "forbidden": I also used the Triband to take pictures in white light, together with the Baader Solar Continuum Filter. The image looked quite dull, but the details were good. The image processing was challenging. It was only afterwards that I discovered the now available Triband manual on Baader's website. The Triband-coating blocks the wavelength of the Solar Continuum Filter – hence the pale image! I should have used an OIII filter. Depending on the focal length extension, the sensitivity of the camera or even the transparency of the sky, a photographic Baader film or the Baader Herschel wedge may be necessary for further light attenuation.
How much of an issue is the obstruction of an SC compared to a refractor? It does reduce contrast, I can see that when I compare the image with that of my refractors. But image processing with dedicated contrast enhancement largely makes up for this disadvantage.
My conclusion:
Highest resolution, that's the goal. With the compact design of an SC, there is also the elegant option to observe at places with better chances for good seing seeing. Because only there can the optics unfold their true potential – and that is amazingly high! A refractor of the same size, on the other hand, will suerly stay at home...
Prominence taken with Baader Triband SCT 9,25", Baader SunDancer TZ-3S, PST Etalon, Player One Saturn M, Seeing 7/10Sunspots AR3311/13/14 in H-alpha-Light taken with Baader Triband SCT 9,25", Baader SunDancer TZ-3S, PST Etalon, Player One Saturn M, Seeing 6-7/10Sunspots AR3323 im H-alpha-Light taken with Baader Triband SCT 9,25", Baader SunDancer TZ-3S, PST Etalon, Player One Saturn M, Seeing 5/10Eruptive Prominence taken with Baader Triband SCT 9,25", Baader SunDancer TZ-3S, PST Etalon, Player One Saturn m, Seeing 7/10Sunspots AR3311 in H-alpha-Light taken with Baader Triband SCT 9,25", Baader SunDancer TZ-3S, PST Etalon, Player One Saturn M, Seeing 7/10Sunsports AR3310 taken with Baader Triband SCT 9,25", Baader SunDancer TZ-3S, Player One Saturn M, Seeing 7/10Eruptive Prominence taken with Baader Triband SCT 9,25", Baader SunDancer TZ-3S, PST Etalon, Player One Saturn M, Seeing 6-7/10
The following statement and pictures were sent to us by our customer Bernhard Hubl.
Hello astrophotographers,
I am pleased to present to you today the First Light with the QHY 268M on the TEC APO 200 FL.
The planetary nebula Abell 12 is perfect for testing the combination of optics, camera and filter in terms of star formation, halos, reflections and sharpness. It is not without reason that Abell 12 has the nickname "Hidden planetary nebula". This faint PN is hidden in the halo of the 4 mag bright star Mu Orionis. Only if all optical components work perfectly together and of course the seeing is favourable, this PN can be imaged well. My plan was to separate the PN cleanly from the bright star with Halpha and [OIII] images. Unfortunately, the weather threw a spanner in the works and so I could only get 3h LRGB. Nevertheless, I am very satisfied with the result.[br]
Original Post from March 17th, 2023
By lucky circumstances I can currently work with a dream optic, a TEC APO 200 FL (fluorite refractor with 200mm aperture).
After unpacking the TEC 200 from the robust transport box, I couldn't wait and had to set up the optics as soon as possible in my small sunroof hut for the first tests. The dimensions of this refractor are really impressive. The interior space of my 2.5x2.5m sliding roof hut is now well utilised 🙂
As I expected for a device of this class, the workmanship is of the highest quality. Although I am only an astrophotographer, I could not resist putting a few eyepieces into the focuser first. Despite less than ideal seeing, the visual impression of the moon and planets was overwhelming. The first test images were taken with my QSI660 camera in very good seeing. Here, the excellent sharpness of the TEC was already apparent and I was able to achieve FWHM values around 1.3" in single 8min exposed luminance images. To ensure the best focus point at all times, I retrofitted the sensitive 3.5" Starlight Feathertouch focuser with the Baader Steeldrive II motor adapter set, an investment that I can recommend without reservation.
Finally, in autumn 2022, I was able to use my Nikon Z6 on the TEC 200 for the first time. Unfortunately, the last few months at my location have been very difficult in terms of clear nights and usable seeing. Therefore, the following images are exposed shorter than I would have wished. However, the results are very convincing, so I don't want to withhold the images from you.
M 33 with TEC200FL + Nikon Z6IC 348 with TEC200FL + Nikon Z6M39 with TEC200FL + Nikon Z6NGC 6940 with TEC200FL + Nikon Z6Mars-occultation on 8.12.2022
In the coming galaxy season, I will use a QHY268 on the TEC200. I am very excited to see what will be possible once the seeing is really good. This image is a small foretaste:
M 64 with TEC200FL + QSI660
Kind regards, Bernhard Hubl
In the spring of 2022, I had the chance to give my opinion on a couple of prototypes of a possible successor to the K-Line filter. The calcium line (CaK) was the only part of the solar spectrum that I had not yet covered with my solar setup. This absorption line is indeed somewhat exotic, and the required filters are not very widely distributed.
The familiar sight of the white-light (continuum) Sun through a Herschel prism or astrosolar film is probably well-known to everyone who has ever tried solar observation. White light is the cheapest and easiest part of observing the sun - in the simplest case, this can even be done by projection as with the [product sku="2903405"]. I have used this part of solar observation for decades, not only through my work at the Observatory in Heilbronn. Especially with monochrome cameras and the improved [product sku="solarcontinuumfilter"], which has been available since autumn 2022, it is possible to get a lot more sharpness and detail when observing the surface of the Sun (the photosphere) in white light, even with the actually modest 80mm aperture that I usually use.
The purchase of the [product sku="1363056"] (and working as a freelancer in homeoffice with free working hours) gave my solar observations another boost. This 0.6Å-filter shows the Sun's chromosphere, so I can see the Sun's "upper atmosphere" – especially the prominences.
And a Calcium-filter? It unveils the border zone – the region between photosphere and chromosphere. Here we can see e.g. the chromospheric network which precedes the formation of sunspots.
Peculiarities of Calcium-Observating
There are some things to keep in mind when observing the Sun in calcium, which is why this is not a very common field of solar observing for amateur astronomers. Most importantly, calcium emits light just below 400 nm, i.e. in the border region between visible light and UV radiation: while younger people can still see these wavelengths to some extent, the ability of older people to do so is declining. Nevertheless, visual observation should be avoided at all costs: The calcium line already belongs to UV radiation, which damages the eye. A UV/IR cut filter already blocks it out for good reason. Calcium filters are therefore purely photographic filters.
And since the calcium-sun emits light so far at the edge of the visible spectrum, the camera has to be able to detect it, too. A normal colour camera like a DSLR or a mirrorless is conceivably unsuitable, since it can detect the two K-lines only with a quarter of its pixels (the sensors for blue) - and is already quite insensitive at 400nm, not least thanks to the usually integrated UV/IR blocking filter, which blocks out blur from the lens in the part of the spectrum that is not visible to us anyway. (Some diagrams for a DSLR can be found at astrosurf.com) Somewhat better are cameras which were converted to full spectrum, where at least the internal filters have been removed; monochrome cameras are ideal. In recent years, smaller mono cameras such as the QHY-III series models have become more common, as they can also be used for autoguiding, where they offer higher sensitivity than their colour versions.
Last but not least, the optics must also be able to handle deep-blue light: Not every telescope delivers good images at that spectral range. Reflecting telescopes have an advantage because they do not suffer from colour aberrations; good ED refractors and Fraunhofer with a slow focal ratio are usually better suited than fast refractors.
The Calcium-Filter
There are two ways for observing the Sun in CaK. On the first hand, you can use similarly narrow-banded filters as they are used for H-alpha observation. In this case, it is even possible to observe prominences in blue light, but the production requirements for the etalon are even higher than for an H-alpha filter - due to the shorter wavelength, it must be even thinner than for an H-alpha filter. Due to the extreme demands, such filters are rare and are usually only offered at short notice when manufacturing capacities are available. Their half band widths (FWHM) are around 2.5Å (0.25 nm) or even less.
Much easier to manufacture and handle are filters with a wider bandwidth. The K-Line Filter 1¼" (gestackt) #2458355 with 8 nm bandwidth and a central wavelength of 394 nm, introduced many years ago, lets both lines through. The chromospheric network can thus already be seen very nicely - and at a fraction of the price of a filter with a half band width (FWHM) of less than a quarter of a nanometre! To achieve this with the techniques available at the time of market launch, two filters were stacked tilted against each other - a comparatively high mechanical effort was added to the manufacturing effort. Important: This filter must be used behind another sun filter with about ND4 and must never be used alone. The scope of delivery of the K-Line therefore included a piece of photographic astrosolar film ND3.8, with which it can also be used on a Newtonian; those who own a refractor with a Herschel wedge and the corresponding damping filters can also use it behind a Herschel wedge.
Well, technology is advancing, and after the good experiences with the CMOS-optimised narrowband filters, Baader also thought about a new version of the K-Line filter. In spring 2022, I was able to test the first production sample to see how it compares to the classic double-stack K-Line, and whether filter stacking with its disadvantages is still necessary today.
The CaK-Sun – old versus new
The new filter was of course compared to the original, stacked K-Line filter. Instead of the photo-version of the Astrosolar-film, which is included with the K-Line-filter, I used a Herschel prism in front of the CaK-filter, and I replaced its ND3-filter with a ND1.8 neutral densitiy filter. This way I could use short exposure times - just as with the AstroSolar film – when using the small monochome-camera which I usually use for autoguiding. For imaging, I used my two main solar telescopes: A Celestron ED80/600 and a Vixen 80/910Mf. Guiding was not necessary: For the first test, I used a Celestron NexStar Evolution mount, which kept the Sun pretty well centered, although I only did a One-Star-Alignment – the different sizes of the images are caused by the remaining drift, which is of course more obvious when you use longer focal lengths. All images were stacked in Autostackert and sharpened in Registax.
At both f/7,5 and f/11, the old K-Line Double-Stack showed the Sun spots, which were also visible in white light, surrounded by an extended chromospheric network, which isn't invisible otherwise. Nice.
So, that's the reference for upcoming filters:
K-Line Double-Stack Filter at an ED80/00 with a Baader Herschel prism and ND1.8 filter.
K-Line Double-Stack Filter at a 80/910 Vixen Fraunhofer with a Baader Herschel prism and ND1.8 filter
[br]
Next try, directly afterwards: the new filter, which was should become the new CaK-filter
At a half band width (FWHM) of 5 nm it is narrower than the old 8 nm K-Line filter, so that the image should be a little bit darker.
The successor of the K-Line Double-Stack Filter – a single filter with modern, CMOS-optimized coatings taken with ED80/600
The successor of the K-Line Double-Stack Filter – a single filter with modern, CMOS-optimized coatings taken with 80/910 Fraunhofer
[br]
The image is a little bit different than that of the original filter: the differences in brightness are not quite as pronounced, while all the details are still clear. Using the depth slider in Photoshop, it is easy to emphasise the differences in brightness a little bit more; for this test, a comparable image processing was more important to me. Since only photographic observations are made, all shots are processed according to one's own preferences anyway.
This already looks very promising. A single modern filter delivers an image that is very similar to the original double stack.
Next test: Let's combine two filters.
Double-Stack: Two filters combined, taken with ED80/600
Double-Stack: Two filters combined, taken with 80/910 Fraunhofer
[br]
The combination of two filters now requires a longer exposure time - but as a result, the image is now almost as dark and contrasty again as with the original double stack. But in comparison with the single new Calcium GEN-II filter, however, there is hardly any improvement in details after the image processing, so the double stack brings no advantages apart from higher costs and a darker image.[br]
Conclusion
[product sku="2961590"]
Who says that everything has to get more and more expensive? With the new Baader Calcium Gen-II Filter, Baader has succeeded in offering the advantages of the old filter at a lower price. So the "blue sun" is now accessible to more observers than ever before.The new calcium filter offers the advantages of the old K-Line filter (high-contrast image with even better filtering), while the disadvantages of the previously necessary filter stacking (darker image, longer exposure times, risk of reflections) disappear.
In contrast to the Solar Continuum filter (but just like the old, stacked K-Line filter), the filter is only available in 1.25", but that is still enough to observe the entire sun in telescopes up to a good 3m focal length. Those who have so far photographed the sun in white light can thus expand their "work spectrum" comparatively cheaply and bring the chromospheric network into the light, which still receive rather little attention, especially in amateur circles.
You don't have to rely on a refractor with a Herschel wedge: With the photographic Astrosolar film ND3.8, you can (just like with the Solar Continuum Filter) also use e.g. a large 8" telescope, no matter if it is a long focal length Schmidt-Cassegrain or a pure mirror system like a Newtonian - this avoides the problems that refractors have with this spectral range, and you can use the entire resolution that optics and atmosphere give.
Of particular interest should be the alternating use of the new [product sku="solarcontinuumfilter"] and the new [product sku="2961590"]
Depending on the camera sensitivity in the respective wavelengths, with a bit of luck the filters can be easily exchanged via filter slider or filter wheel, so that comparison images in white light (Solar Continuum) and CaK are possible promptly without having to adjust the camera alignment. Since stacking is not required, both filters also fit into flat filter mounts and thus into common filter sliders/wheels.
Bonus
I also had the opportunity to take a look behind the scenes of filter development and try out a really impressive filter: A 1,2nm K-Line-Filter!
The Sun with 1,2nm half band width (FWHM) instead of 5 nm!
At this half band width (FWHM), almost nothing but the CaK-light remains – and the chromospheric network is much more obvious!
But there is a price to pay – much, much higher costs of production. In series production, this filter would cost at least 8 to 10-fold as much as a 5nm calcium filter and would only be something for absolute specialists. However, despite the narrow bandwidth, it still does not show any prominences in the CaK (more precisely, you can detect them - but beautiful is something else). Since it is closer in price to an even narrower-band, but ultimately more versatile heated CaK SolarSpectrum filter (which are occasionally available, depending on production capacity) than to simple calcium filters, it will remain a prototype. But the development continues - I am curious to see what else awaits us in the next few years.
I had the chance to test the DeltaRho 350 f/3 Astrograph (DR350) with the serial number 0003 – all in all this solution is absolutely remote capable! You can read my first impressions and experiences here:
Setup and installation
The unit is very well made and in combination with PlaneWave's focuser and de-rotator, it is quite a massive unit and surprisingly heavy. The center of gravity is at the back of the telescope.
The PWI4 (beta) software that operates the DR350 telescope installs quickly and works immediately with Maxim DL. If you have problems, take a look at the USB settings in PWI4, which is used to operate the fans, the heating of the secondary and primary mirrors, the focuser, and the rotator. The DR350 is controlled purely by the software.
With Maxim DL, I have been able to perform every working routine of focusing and field tilt measurement very well. The results are consistent and extremely important for accurate alignment! After I attached the [product sku="1931162"] with the help of the Baader M68 system, the DR350 was ready for use.
There is a saying among astronomers that with a new hardware the weather is bad for many weeks... Now I have to give some credence to this, because due to high and ground fog, or clouds that did not have a gap, the process of adjustment dragged on for a long time... and the first result was still far away.
The adjustment procedure before the First Light
The bottom line is that the adjustment is easy to do - but it is very important that the image fits! The primary and secondary mirrors are laser-aligned at PlaneWave in the US; the secondary and the tilter must then bring the camera into optimal alignment. TIP: The night must be good and clear for the field tilt measurement results to be correct! In case of haze, fog or clouds I advise against it![br]
Following are my steps in an overview to get the DR350 to work.
Determine the focus! Use a normal focus routine. The focus point that you have determined must be used as a basis for the field tilt measurement.
The field measurement: For this I use a total of 5 shots: two before and two after the focus, plus one corresponding to the entered base value. The distances are 500 steps each at Bin2!
From this the best focus is now determined. The evaluation shows the field and how the tilt is. Afterwards the field can be corrected either at the PW-Tilter with the platelets or with the Baader M68-Tilter (if it is available in the system).
And now: run the routine again and repeat the steps of the adjustment until the deviation is below 5micron!
Check the center of the secondary mirror at Bin1, if all in all is exactly centered!
Then do one last final pass with the focus / field tilt routine!
Once I had achieved the values that Planewave specifies, imaging began!
The Basics
For each shot, I paid attention to the following points:
Cool-down: This is where I run the fans until the difference between ambient and catch + primary mirror is less than 1.5°C;
I did not have any fan active during the exposures!
The mirror heaters were in use when I had a lot of dew (unfortunately often). But they only ran until the mirror was completely clear again; then it was brought back to temperature with the side fans!
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First Light
I shot in luminance and with RGB (the new Baader LRGB CMOS optimized filter are just top!). I compared the focus in Lum with R/G/B, again the system is very balanced, there is not much variation in the values.
Now I just had to have a really good night with no moon (not a good combination at f/3), and good to very good conditions. Often there was good weather until the end of twilight, but then very often it became difficult. (Fog formation!)
The image of IC59 and IC63: Here the conditions were good for red, just good for green, and for blue I unfortunately already had a lot of haze and ground fog. Exposures were only 60sec per single shot, with the QHY 600M in Bin2 (Gain 26).
The number of all exposures was well over 100, leaving 74min in RGB. The flats were taken with film, darks and bias for data reduction in PixInsight.
The result is very promising with the background of not ideal conditions! For ONLY RGB this is really good!
Software: Data reduction, stacking: PixInsight
Image editing: Adobe Photoshop CC 2023 + APF-R
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My first CONCLUSION
It is a top hardware, which needs absolute care with the adjustment, but rewards you with very good image results. And the system is absolutely remote capable!